A great deal of research has been conducted on methods for improving the chemical resistance and impact strength of polycarbonates by the use of siloxane monomers. However, these methods may result in a considerable deterioration in the transparency of polycarbonates due to incompatibility of the polycarbonates with siloxane monomers upon copolymerization.
Many efforts have been made to solve the problem of incompatibility between polycarbonates and siloxane monomers and to utilize the beneficial aspects of the silicon atoms of siloxane monomers in terms of chemical resistance and impact strength. For example, studies are currently being undertaken into the preparation of oligodimethylsiloxane-polycarbonate copolymers in which silicon atoms of the siloxane monomer are uniformly distributed in the polycarbonate.
U.S. Pat. No. 3,189,662 issued to Vaughn et al. discloses a method for preparing a copolymer of polycarbonate and a siloxane monomer in which bisphenol moieties are bound to both ends of polydimethylsiloxane. However, hydrolysis of the siloxane monomer is likely to occur after polymerization due to the unstable silicon-oxygen bonds connecting the siloxane and reactive moieties, leading to poor weather resistance and mechanical properties of the copolymer.
In attempts to solve such problems, there have been developed monomers with improved hydrolysis resistance in which propylphenylhydroxysiloxane blocks containing a silicon-carbon bond instead of a silicon-oxygen bond are linked. Monomers using silicon-aryl bonds have been developed in the early days (see U.S. Pat. No. 5,243,009). Since then, monomers with improved heat stability and hydrolysis resistance having silicon-alkyl bonds have been developed.
However, no methods have as yet been developed for the preparation of siloxane monomers in which various moieties such as alkyl are introduced between oligodimethylsiloxane blocks to achieve improved physical properties, for example, good resistance to heat and hydrolysis, because there are no successful synthetic methods for introducing new moieties between oligodimethylsiloxane blocks.